Photonic Crystal Fibre Attenuation
Photonic crystal fibres take the properties of traditional silica to new dimensions, from the exploitation of the high optical nonlinearities of PCF in supercontinuum generation, to the low mid-infrared attenuation of hollow core PCF, a spectral region of increasing interest for applications in spectroscopy and medicine given strong target absorption bands and the emergence of new generations of mid-IR laser sources.
The spectral attenuation of PCF (300-2700nm) and hollow core PCF (2000->4000nm) is measured by the cut-back technique using a Bentham DTMc300 triple-grating double monochromator with motorised slits, and fibre connectorised input, configured for the range 300-5000nm.
Fully automated grating control, detector selection and slit adjustment for constant bandwidth gives simple operation over this broad spectral range. The sensitive detection gives a good signal to noise even with a black body source and a single-mode fibre. In the mid-IR, the use of a cryogenically cooled InSb detector allows the accurate measurement of attenuation even in this unfavourable wavelength range.
Inset: transmission spectrum through 83 m fibre (blue) and transmitted HeNe laser spectrum (red, 0.5 nm resolution) through 78 m of fibre.